Insulator pad for upholstered furniture

ABSTRACT

An insulator pad for upholstered furniture consisting of a fabric sheet including a pair of side strands of tubular plastic material, and a series of spaced apart resilient spring steel wires extending between said side strands, the cross wires being knotted tightly about the side strands in indenting relation thereto.

United States Patent n91 Arnold Feb. 1 l, 1975 INSULATOR PAD FOR UPHOLSTERED 3.024. 2 1 24 3 ,|32,3 1 64 FURNITURE 3,428,975 2/1969 [75] Inventor: Harmon W. Arnold, Carthage, Mo. 3,733.625 5/1973 [73] Assignee: Flex-O-Lators, Ine., Carthage, Mo.

i Primary Examiner-William E. Schulz [22] Filed May 1973 Attorney, Agent, or Firm-John A. Hamilton [2]] Appl. No.: 357,249

[57] ABSTRACT 5/354 An insulator pad for upholstered furniture consisting Fie'ld 75' 5/354 of a fabric sheet including a pair of side strands of tu- 5/186 297/457 bular plastic materiaL'and a series of spaced apart resilient spring steel wires extending between said side strands, the cross wires being knotted tightly about the [56] Reerences Cited side strands in indenting relation thereto.

UNITED STATES PATENTS 1l/l957 Hammond 5/354 3 Claims, 5 Drawing Figures 1 INSULATOR PAD FOR UPI'IOLSTERED FURNITURE This invention relates to new and useful improvements in accessories for use in upholstered furniture, and has particular reference to insulator pads, which are fabric sheets including rather closely spaced'spring wires, the fabric being used by inserting it between the coil spring base or other spring deck of automotive or furniture seating and the overlying layers of padding material, which usually consists of fibrous material such as cotton batting, or natural or synthetic foam rubber material. The function of the insulator pad is to provide a smoother, more continuous base for the padding than is commonly provided by the coil springs or other spring units of the spring deck, and to prevent said padding from working down into the spaces between or withinthe spring deck units.

An extremely common form of insulator pad in very wide usage has been one in which the side strands consist of twisted kraft paper cords, with the cross wires twisted or wrapped tightly about the side strands in indenting relation. The paper of the side strands provided good purchase for the cross wires thereon, so that the loops of said cross wires encircling the side strands could not slide therealong, and properspacing of the cross wires was maintained during usage, in the portions thereof adjacent the side strands.

However, while paper is the traditional material used for the side cords, paper for this purpose is becoming increasingly difficult to obtain, so much so that manufacturers of the pads have great difficulty in supplying their requirements. Furthermore, paper cord in this usage does have certain shortcomings from a functional viewpoint. For example, paper, in long periods of usage, tends to dry out and shrink, with the result that the loops of the cross wires slide along the side cords and the spacing of the crosswires is lost. When the spacing between the cross wires becomes uneven, the support of the overlying padding becomes uneven, so that the cushion presents an uneven, lumpy appearance. Also, some of the cross wires may contact each other, so that rubbing, grating or squeaking wire noises can occur.

Attempts to use side strands of material other than paper have been made, notably of plastics, but have also been subject to certain disadvantages, due primarily to the difficulty of finding a material with the proper combination of resistance to cutting by the cross wires, with the ability to be indented by said wires. Softer plastics, such as low-density polyethylene, tended to be sliced or cut by a tempered spring steel cross wire as said wire was wrapped tightly or knotted thereabout, which was of course completely unsatisfactory, since even if the side cord was not completely severed, it was so seriously weakened that it would easily break under the repeated flexures of normal usage. The use of a harder plastic material in the side cords, in solid rod form, eliminates cutting thereof by the cross wires, but was unsatisfactory because by very reason of its hardness it also resisted indentation by the cross wires as they were knotted thereabout, any such indentation being insufficient to prevent the loops of the wires from sliding along the cord under the stresses of normal usage.

It has now been found, however, that a relatively hard plastic material in tubular form makes an ideal side cord in the structures discussed. The hardness of the material effectively resists cutting thereof by the cross wire's as they are knotted thereabout, while at the same time the hollow cores of the cords provide space allowing the wall thereof to yield or collapse locally under the wire, so that the loop of the wire is effectively anchored against sliding movement along the cord.

Tubular plastic cords may also be utilized as intermediate cords of the pad, which extend parallel to and intermediate the side strands, and are pierced by the cross wires, having the function of maintaining proper spacing of the cross wires intermediate the side strands, but since here the cross wires pierce the intermediate strands, there is no problem of cutting or indentation of said strands, and a softer plastic may be used. In fact, a softer plastic is preferred at this point, since when pierced by the cross wires, its softness provides a better frictional resistance to sliding thereof along the wires.

Accordingly, the principal object of the present invention is the provision of an insulator pad for upholstered furniture consisting of generally parallel side strands with cross wires of spring steel extending be tween and wrapped tightly at their end portions about said side strands, said side strands being formed of a flexible plastic material.

Another object is the provision of an insulator pad of the character described wherein said side strands each constitute a hollow tube of flexible plastic material, the plastic material being sufficiently hard to prevent cut ting thereof by a cross wire as said wire is wrapped tightly thereabout, while the hollow core of the tube permits the wall. thereof to collapse locally under the pressure of the wire, in order to prevent slippage of the wire along the tube.

Other objects are simplicity and economy of construction, and efficiency and dependability of operation.

With these objects in view as well as other objects which will appear in the course of the specification, ref erence will be had to the accompanying drawing, wherein:

FIG. 1 is a fragmentary top plan view, partially broken away and foreshortened, of an insulator pad for upholstered furniture embodying the present invention,

FIG. 2 is an enlarged fragmentary sectional view taken on line IlIl of FIG. 1,

FIG. 3 is an enlarged fragmentary sectional view taken on line III--III of FIG. 1,

FIG. 4 is a view similar to FIG. 3, but showing a modifled form of wire knot, and

FIG. 5 is an enlarged fragmentary sectional view taken on line VV of FIG. 1.

Like reference numerals apply to similar parts throughout the several views, and the numeral 2 applies generally to the insulator pad forming the subject matter of the present invention. It comprises a planar fabric sheet consisting of a pair of generally parallel side strands 4, and a continuous series of generally parallel, spaced apart, spring steel cross wires 6 extending transversely between said side strands, each cross wire being tightly wrapped at its opposite ends about the respective side strands to form a know 8. In some applications, it may be desirable to fasten the wires still more securely to the side strands by twisting the extreme end portions of each wire about the standing portion thereof, as indicated at 10 in FIG. 4. Also the pad may include one or more intermediate strands 12 disposed between and parallel with the side strands, each cross wire-6 piercing each intermediate strand 12 at its point of intersection therewith, as shown in FIG. 5. In use, the pad is inserted between the spring deck or base of a seat structure, and the overlying layers of padding material, and has the primary functions of providing a smoother, more even support for thepadding", and preventing the padding material from working down into the spaces within and between ,the spring elements of the deck. A spacing of about one inch between crosswires 6 has been found effective for this purpose. The area dimensions of the pad are generally such as to cover the entire top area of the spring deck.

Commonly, cords of twisted kraft paper have been utilized both as the side and intermediate strands of the pad above described. Such cords can be easily pierced by the cross wires when used as intermediate strands, and indented by the cross wires when said wires are knotted thereabout in their use as side strands, to preventslippage of the wire loops along the side strands. Prevention of displacement of the wires along the side and intermediate strands is necessary in order to preserve proper spacing of the wires during use. However,

in view both of the growing scarcity of paper for this purpose, and of the functional shortcomings of paper in drying and shrinkage, as already discussed, it has become expedient to develop the use of some other material in the side and intermediate strands.

Plastic is a logical alternative to the paper cords, since it does not dry out and shrink as does paper, and is relatively easily available, but its use presented certain problems. The cross wires are bent or knotted around the side strands very tightly, necessarily tightly enough to indentsaid side strands. Since the cross wires are of tempered spring steel, and since the side strand itself must serve as the anvil around which the bending of the wires is performed, the bending of the wires results in an extreme, localized pressure of the wires against the side strand, with a strong tendency to cut or sever the side strand. While the fibrous nature of paper allowed it to resist cutting by this pressure, plastics commonly used in comparable applications, such as low-density polyethylenes having a Shore Durometer hardness of about D-47, were easily cut in the present application. Even a partial or incomplete severance of the side cord so weakens it that it will break after relatively short periods of use.

This susceptibility of softer plastics to cutting suggested the use of a harder plastic material, plastics of sufficient hardness to resist such cutting being readily available. However, when such hard plastics were experimented with, it was found that they were also so dense that they resisted indentation by the wire knots to such an extent that the knots were not firmly anchored in place, but could slide more or less freely along the hard plastic side cords under the stresses of normal usage.

According to the present invention, it has been found that a fully satisfactory combination of hardness to resist cutting, and yieldability to permit indentation, can be obtained by the use of a relatively hard plastic tube as the side strand material. The hardness successfully resists cutting, while the hollow core of the tube provides space allowing the tube wall to collapse or restrict locally under the wire pressure as each wire is knotted thereabout, so that the loop of wire is firmly anchored against sliding along the tube. The tubular form of the side strands is clearly shownin the drawing, the hollow interior passagev thereof being indicated at 14, the passage being restrictedas at 16 within the loop or knot 8 of each cross wire. Plastic tubes may also be used as intermediate strands 12, as shown, but since here there is no problem of providing the proper combination of hardness to prevent cutting and yieldability to permit indentation, a softer plastic may be used. in fact, a

softer plastic provides a better frictional"resistance to the sliding of strands 12 along the cross wires than would a harder plastic.

The specific dimensions and properties of the plastic tubing used in side strands 4 are not highly critical, and any of several different materials could be used, as long as they possess the requisite hardness, and the required flexible yieldability when in tubular form. However, extensive testing has indicated optimum efficiency, together with reasonable cost, can beobtained by the use of a high-density polyethylene material. Such a resin typically has a Shore Durometer hardness of about D-64, a density of about 0.95g./cu.cm., a melt index of around.0.25 g./l0 min., a tensile yield strength in the range of 3,500-4,000 p.s.i. and'elongation of about percent. With this material good anchoring of the cross wire knots 8 is obtained with tubing of 0.156 in. outside diameter and 0.0625 0.090 in. inside diameter, and cross wires of 19 M20 gauge oil tempered spring steel. Specific tubing properties and dimensions can be determined experimentally in each application. In other words, best results are obtained with the plastic material given if the plastic side strands are roughly four times the wire diameter, and if the inside tube diameter is about 40-60 percent of the outside tube diameter.

While I have shown and described a specific embodiment of my invention, it will be readily apparent that many minor changes of structure and operation could be made without departing from the spirit of the invention.

What I claim as newand desire to protect by Letters Patent is:

l. Anv insulator pad for upholstered furniture comprising a planar fabric sheet including:

a. a pair of generally parallel side strands each consisting of a hollow tube of flexible plastic material, and

b. a series of generally parallel, spaced apart resilient spring wires extending transversely between and knotted at their respectively opposite ends about said strands, said side strand material being of such hardness and density that if said strand were solid, it would prevent appreciable indentation thereof by said cross wires, the hollow interiors of said side strands permitting localized collapse of the walls thereof within the knots of said wires, said knots therefore appreciably indenting the exterior surfaces of said side strands.

2. A pad as recited in claim 1 wherein the plastic material of the side strands constitutes a high-density polyethylene resin having a Shore Durometer hardness of about D-64.

3. A pad as recited in claim 2 wherein the inside diameter of each side strand tube is about 40-60 percent of its outside diameter, and the outside diameter is about four times the diameter of each cross wire. 

1. An insulator pad for upholstered furniture comprising a planar fabric sheet including: a. a pair of generally parallel side strands each consisting of a hollow tube of flexible plastic material, and b. a series of generally parallel, spaced apart resilient spring wires extending transversely between and knotted at their respectively opposite ends about said strands, said side strand material being of such hardness and density that if said strand were solid, it would prevent appreciable indentation thereof by said cross wires, the hollow interiors of said side strands permitting localized collapse of the walls thereof within the knots of said wires, said knots therefore appreciably indenting the exterior surfaces of said side strands.
 2. A pad as recited in claim 1 wherein the plastic material of the side strands constitutes a high-density polyethylene resin having a Shore Durometer hardness of about D-64.
 3. A pad as recited in claim 2 wherein the inside diameter of each side strand tube is about 40-60 percent of its outside diameter, and the outside diameter is about four times the diameter of each cross wire. 